Liquid electrophotographic (LEP) printing uses a liquid ink for printing on substrates rather than using a dry, powder toner. Common examples of LEP printing machines are the HP® digital Indigo™ printing presses. The toner particles in the liquid ink used in LEP printing are sufficiently small such that the LEP-printed images do not mask the underlying surface roughness/gloss of, for example, paper substrates. The liquid ink (also referred to herein as “ink”, “liquid toner”, or “LEP ink”) used in LEP printing is a suspension of small pigment particles in the range of about 1 to 2 microns in a nonaqueous liquid. HP® ElectroInk® is a commonly used liquid ink for liquid electrophotographic printing. Pigment particles can mean pigment dispersed in polymer. LEP printing is considered to give some of the best digital print quality images at a relatively rapid speed.
However, it has been found that oftentimes LEP printed images will not adhere to substrates as well as images printed using electroreprographic printing methods that utilize a dry-toner process. Many of the issues with LEP printing are described in WO2013030784, which is hereby incorporated by reference herein in its entirety. Therefore, a need exists to enhance the adhesion of LEP ink on substrates via the LEP printing process.